package com.kfm.base.collection;

import java.util.HashMap;

public class Demo15 {

    public static void main(String[] args) {
        HashMap<String, Integer> map = new HashMap<>();

        map.put("a", 1);
        map.put("b", 2);
        map.put(null, null);

        System.out.println(map);
    }
}
